Soft-demodulation based waveform repair for signals undergoing spectral suppression

Abstract

Systems and methods for waveform repair. The methods comprise: receiving a signal of interest having a spectral distortion, the signal of interest having a sequence of symbols; generating an estimate for each symbol of a sequence of symbols in the signal of interest; and applying reconstruction filtering to the estimates to correct the spectral distortion.

What is claimed is: 
     
         1 . A method for waveform repair, comprising:
 receiving a signal of interest having a spectral distortion, the signal of interest having a sequence of symbols;   generating an estimate for each symbol of a sequence of symbols in the signal of interest; and   applying reconstruction filtering to the estimates to correct the spectral distortion.   
     
     
         2 . The method according to  claim 1 , further comprising performing band-rejection filtering to remove the interference from the signal of interest. 
     
     
         3 . The method according to  claim 2 , wherein the estimate comprises a maximum a posteriori probability estimate, or an appropriate approximation thereof, for each symbol of a sequence of symbols that is generated using an output signal of the band-rejection filtering. 
     
     
         4 . The method according to  claim 2 , wherein the reconstruction filtering is applied to the estimate to demodulate a portion of the signal of interest which was removed by the band-rejection filtering. 
     
     
         5 . The method according to  claim 4 , further comprising:
 combining the band-rejection filtered portion of the signal of interest with the output signal of the reconstruction; and   performing upconversion and bandpass filtering using a resulting signal from said combining to reconstitute the signal of interest without interference.   
     
     
         6 . The method according to  claim 2 , wherein the band-rejection filtering comprises notch filtering. 
     
     
         7 . The method according to  claim 6 , wherein the notch filtering is shaped to minimize the energy of the intersymbol interference. 
     
     
         8 . The method according to  claim 1 , wherein the estimate for each symbol is generated using at least one past symbol that comes before the symbol in the sequence of symbols or at least one future symbol that comes after the symbol in the sequence of symbols. 
     
     
         9 . The method according to  claim 1 , wherein the estimate is generated using a BCJR algorithm. 
     
     
         10 . The method according to  claim 1 , wherein the reconstruction filtering comprises bandpass filtering. 
     
     
         11 . A circuit, comprising:
 a soft symbol demodulator configured to generate an estimate for each symbol of a sequence of symbols in a received signal of interest having a spectral distortion; and   a reconstruction filter configured to apply reconstruction filtering to the estimates to correct the spectral distortion.   
     
     
         12 . The circuit according to  claim 11 , further comprising a frequency excision module configured to perform band-rejection filtering to remove the interference from the signal of interest. 
     
     
         13 . The circuit according to  claim 12 , wherein the estimate comprises a maximum a posteriori probability estimate, or an appropriate approximation thereof, for each symbol of a sequence of symbols that is generated using an output signal of the band-rejection filtering. 
     
     
         14 . The circuit according to  claim 12 , wherein the reconstruction filtering is applied to the estimated to demodulate a portion of the signal of interest which was removed by the band-rejection filtering. 
     
     
         15 . The circuit according to  claim 14 , further comprising:
 a combiner configured to combine the demodulated portion of the signal of interest with the output signal of the band-rejection filtering; and   a filter configured to perform upconversion and bandpass filtering using an output signal of said combiner to reconstitute the signal of interest without interference.   
     
     
         16 . The circuit according to  claim 12 , wherein the band-rejection filtering comprises notch filtering. 
     
     
         17 . The circuit according to  claim 16 , wherein the notch filtering is shaped to minimize the energy of the inter-symbol interference. 
     
     
         18 . A non-transitory computer-readable medium that stores instructions that, when executed by at least one computing device, will cause the at least one computing device to perform operations comprising:
 receiving a signal of interest having a spectral distortion, the signal of interest having a sequence of symbols;   generating an estimate for each symbol of a sequence of symbols in the signal of interest; and   applying reconstruction filtering to the estimates to correct the spectral distortion.   
     
     
         19 . The non-transitory computer-readable medium according to  claim 18 , wherein the at least one computing device is configured to perform band-rejection filtering to remove the interference from the signal of interest. 
     
     
         20 . The non-transitory computer-readable medium according to  claim 19 . wherein the estimate comprises a maximum a posteriori probability estimate, or an appropriate approximation thereof. for each symbol of a sequence of symbols that is generated using an output signal of the band-rejection filtering.